In the summer, I strongly recommend touring the parks beginning first thing in morning, at rope drop. You'll get the most rides completed in the shortest time possible this way, because the first hour a park is open is its least crowded time. Also, expect daily afternoon or evening rains in the summer. Morning is the one time of day in summer that you can typically count on it to stay dry. Try to get your outdoor rides completed in the morning, and schedule your outdoor FP+ rides for the morning, as well.
Mid-day, when it's really hot and/or rainy, is a great time to return to your resort. You can use the time to nap or swim, depending on the weather. One annoying thing about Disney resorts is that they have minimal entertaining programming on the resort room tvs, and only club level rooms have dvd players, so if you want to spend some of your down time being entertained in the resort room, you might want to bring a portable dvd player with you.
Evening, when it's dry, is a good time to go to the parks to watch the evening fireworks shows or do more attractions. Evening Extra Magic Hours are great, too. In fact, summer is a particularly good time to make use of both morning and evening EMH, because the weather is better in early morning and late evening than it is mid-day.
But do what appeals to you. We're taking a 4-night getaway this August before school begins, and got 1-day park hopper plus tickets so that we can have one long day hopping from park to park (we'll have ponchos & waterproof shoes to help us power through the rain, and I carry a small UV umbrella as a parasol to provide shade as we tour), two days for Disney's great water parks, and one full day to just lounge around the resort and swim. But even on more active days, we almost always swim. The Disney deluxe feature pools are great.
Hope this helped a bit. Have fun!